/*
 * Copyright 1999-2020 Alibaba Group Holding Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.alibaba.csp.sentinel.log;

import java.util.HashMap;
import java.util.Map;
import java.util.ServiceLoader;

import com.alibaba.csp.sentinel.util.StringUtil;

/**
 * SPI provider of Sentinel {@link Logger}.
 *
 * @author Eric Zhao
 * @since 1.7.2
 */
public final class LoggerSpiProvider {

	private static final Map<String, Logger> LOGGER_MAP = new HashMap<>();

	static {
		// NOTE: this class SHOULD NOT depend on any other Sentinel classes
		// except the util classes to avoid circular dependency.
		try {
			resolveLoggers();
		} catch (Throwable t) {
			System.err.println("Failed to resolve Sentinel Logger SPI");
			t.printStackTrace();
		}
	}

	public static Logger getLogger(String name) {
		if (name == null) {
			return null;
		}
		return LOGGER_MAP.get(name);
	}

	private static void resolveLoggers() {
		// NOTE: Here we cannot use {@code SpiLoader} directly because it depends on the
		// RecordLog.
		ServiceLoader<Logger> loggerLoader = ServiceLoader.load(Logger.class);

		for (Logger logger : loggerLoader) {
			LogTarget annotation = logger.getClass().getAnnotation(LogTarget.class);
			if (annotation == null) {
				continue;
			}
			String name = annotation.value();
			// Load first encountered logger if multiple loggers are associated with the
			// same name.
			if (StringUtil.isNotBlank(name) && !LOGGER_MAP.containsKey(name)) {
				LOGGER_MAP.put(name, logger);
				// System.out.println("Sentinel Logger SPI loaded for <" + name + ">: "
				// + logger.getClass().getCanonicalName());
			}
		}
	}

	private LoggerSpiProvider() {
	}
}
